Honeywell motorised valve faults

Common Honeywell motorised valve types

Honeywell make a large range of motorised valves used in domestic central heating systems. The most common by far are the 22mm 3-port, 5-wire, mid-position valve and the 22mm 2-port, 5-wire, zone valve. These 22mm valves (3-port V4073A1039 and 2-port V4043H1056) are used in smaller and medium sized properties.

In larger properties, 28mm valves may be used (the 5-wire 3-port V4073A1088 and the 6-wire 2-port V4043H1106). The 28mm V4043H1106 2-port zone valve has a 6th wire, coloured white. This white wire might not be used. In that case it should be made safe electrically.
These valves have compression pipe connections, though Honeywell make motorised valves with threaded connections too.

How motorised valves are used

Typically, a small or medium sized property will have either one 3-port valve (which splits the central heating water flow between cylinder and radiators) or two 2-port valves (one governing flow to the cylinder and one governing flow to the radiators).

When using a 3-port valve, the control system may be known as a Sundial Y Plan system or a Honeywell Y Plan system.
When using two 2-port valves, the control system may be known as a Sundial S Plan system or a Honeywell S Plan system.
The Y Plan and S Plan names are more commonly used when other Honeywell controls are also used (programmer, room thermostat, cylinder thermostat and wiring centre).

If the property uses a combi boiler (rather than a heat-only boiler) the boiler will usually contain a diverter valve. In small properties there may be no other motorised valves.
In medium sized or larger properties, using a combi boiler, there may be an additional zone valve external to the boiler which allows the heating to be split into two zones.
System boilers may also have a diverter valve or zone valve built into them and might not have any external zone valves.

Under Part L of the Building Regulations, many new properties must have the heating radiators (or underfloor heating) split into two zones. This creates a living zone and a sleeping zone which both have separate time and temperature controls to improve energy efficiency.

Honeywell V4073A1039 22mm 3-port mid-position motorised valve
Honeywell V4073A1039 22mm 3-port mid-position diverter valve. These are 5-wire valves. When used with other Honeywell controls the setup is know as Y Plan

In normal operation, with a heat-only boiler, central heating water is heated in the boiler and then pumped round the system by a circulating pump. Motorised valves are used to split or divert the flow. The heated water can either be sent to the radiators (or underfloor heating) or to the cylinder coil to heat the domestic hot tap water. The cooled circulating water is then returned to the boiler to be heated again.

A programmer and room thermostat (stat) are used to control heating times and room air temperatures. The programmer and room stat may be combined into a single programmable room stat.
A programmer and cylinder thermostat (stat) are used to control the times when the hot water is heated and to control the maximum temperature of the stored hot water.

In smaller properties there is usually one programmer which has two channels. One programmer channel controls the heating (radiators or underfloor) and the other programmer channel controls hot water. Where additional zone valves are used there will usually be another programmer or timer.

Honeywell motorised valve construction

Nearly all Honeywell valves have a powerhead (also called an actuator) which can be separated from the valve body. The valve body is the brass casting which is bolted into the pipework.

The powerhead or actuator is the electrical section. It’s comprised of a motor and some electronic components and usually has one or more microswitches.
These are contained within a silver coloured metal box which is connected to the brass body.

The powerhead drives a spindle (or actuator shaft) which is part of the valve body.

On modern Honeywell valves, if the powerhead fails it can be removed from the valve body without draining down. However, be warned! With very old Honeywell motorised valves the powerhead could not be removed without draining the water first.

We think these older valves are pre-1985 and that seems to be backed up by this note in the Honeywell Flow Solutions pdf:
“On older style valves pre-1985, which do not have the replaceable head feature, the adaptor plate assembly can be used to upgrade the valves, to allow the replaceable powerhead to be used.”

We also think that all the removable powerheads carried the “pip” (or raised bump) on the top of the powerhead metal case, but we are not certain of this.

Metal cover of a Honeywell valve actuator, showing raised bump or pip
The raised bump or pip on the metal cover of the powerhead or actuator of a Honeywell motorised valve

Removing a Honeywell motorised valve powerhead

Check that the valve is not so old that the system needs to be drained before removing it. As far a we know, Honeywell motorised valves which were made from 1985, and which carry the raised pip (small bump) on the top of the metal cover, allow the powerhead to be removed without draining down (see above).

Isolate all electrical power to the central heating system and test to ensure that it is electrically safe. We use a non-contact volt stick to confirm that it is safe. Non-contact voltage testers are much safer to use than traditional neon testers. The ones we use are made by Fluke.

White tipped, orange and grey, pen-shaped voltage tester
Non-contact voltage tester made by Fluke. The entire casing is plastic and there are no exposed metal parts

Move the valve’s manual lever to the manually open position. (Push it towards the MAN OPEN end of the slot and lift while releasing it, so it settles into the hook at the top of the slot.)

With the power off, release the powerhead cover retaining screw and lift away the metal cover. You don’t need to take the cover screw all the way out. Recent valves have an internal earth wire which connects the cover to the powerhead. Once the cover has been lifted clear it can be hung to one side. With earlier valves, the cover was completely free.

Cover securing screw on Honeywell motorised valve actuator or powerhead
Honeywell valve powerhead cover release screw. The powerhead may also be called the actuator

When the cover is removed you have access to the two screws which secure the powerhead.
These screws are diagonally opposite each other and pass through the steel base plate of the powerhead (actuator) into the brass flanged top of the valve body.

Unscrew both of these screws. They don’t usually come right out of the steel plate but are retained by it as the powerhead is lifted away from the valve body.

One of two screws which hold Honeywell valve powerhead to the body
One of two screws which hold the powerhead to the valve body. They are diagonally opposite each other

Motorised valves are often fitted in tight spaces with limited visibility so note the orientation of the powerhead.

It will make it easier when re-fitting it (just remember which end the flex was connected or take a picture on your phone). The powerhead can only fit one way round onto the valve body but if space is tight that might not be obvious.

With the powerhead cover removed you also have access to the screw which retains the motor. The motor can, if necessary, be removed without disconnecting the powerhead from the valve body.

However, if you need to replace the motor it may be easier to remove the powerhead so you can work on it in the open. Remember, on early Honeywell motorised valves (pre-1985) you can’t remove the powerhead without draining down first!

The commonest fault with Honeywell motorised valves is motor failure.

Honeywell valve motor fault? Testing a Synchron valve motor

The electronics in Honeywell motorised valves tend to be quite stable and show relatively few faults but the motor may fail after years of operation. Honeywell use Synchron motors and these are freely available but there are lots of cheap cloned motors out there. These look identical but, instead of the name SYNCHRON, they use the word Synchronous.

These are all synchronous motors (synchronous is a generic term for a type of electric motor). However, only Synchron have the right to call their synchronous motors “SYNCHRON”. There’s usually a clue in the price. Most of the clones cost about half the cost of a genuine SYNCHRON motor. We never use cloned motors. We tried in the past and, in our experience, they fail really quickly.

As far as we know, the genuine SYNCHRON motors made for Honeywell have two blue wires whereas most genuine SYNCHRON motors have orange wires. In the past, Honeywell told us that the motors made for them produced a higher level or torque than the standard SYNCHRON motor.

Two almost identical genuine Synchron motors
Both of these genuine SYNCHRON motors work in Honeywell motorised valves. The motors SYNCHRON make specifically for Honeywell come with two blue wires

Replacement Honeywell SYNCHRON motors are available but are a bit more expensive. For a long time we’ve used the standard SYNCHRON motors as replacements, with very few problems.

Synchron valve motors can remain energised and hot for many hours a day, all through the winter. They may eventually fail. A failed Synchron valve motor will prevent a 2-port motorised valve from working. The valve won’t be driven open and the end switch will not be made (connected) so power will not be sent on to the boiler or pump.

If you know how to work safely with mains voltage electricity, the valve motor can be tested with a multimeter. With the mains electrical supply turned off and isolated, the resistance across the two motor wires (either both blue or both orange) can be tested. To test correctly, at least one of the two motor wires must be disconnected from the heating wiring circuit.

We find it is normally about 2.1kΩ (2100 ohms) if the motor is cold and up to 2.4kΩ (2400 ohms) if the motor is quite warm. I think that a reading anywhere between 2.0kΩ (2000 ohms) and 2.5kΩ (2500 ohms) suggests that the motor windings are probably OK. If the reading is many times higher than that, or it is open circuit, the motor has failed.

There are lots of poor quality synchronous motors out there. If the motor cap says “Synchronous” rather than “SYNCHRON ®” it may cost less than half but you’ll probably be changing it again before long!
Travis Perkins were selling BOSS brand genuine SYNCHRON motors in the past but their web page photo now shows what looks to me like a cloned motor. ACL Drayton motors seem to still be genuine SYNCHRON and let’s hope it stays that way. You’ll have to check.

Changing a Honeywell valve motor

Replacing a failed Synchron motor in a Honeywell motorised valve is quite straightforward, assuming you know how to work with mains electricity safely. Make sure you read the whole process through before starting!

First, isolate all electrical power from the central heating system controls. Then, using a non-contact voltage tester like the Fluke volt stick above, check that the system is safely isolated.

It may be easier to have the valve set in the manually open position using the manual lever. (See Honeywell Motorised Valve Manual Lever, below.)

Remove the metal cover of the powerhead by removing the cover securing screw, then lift the cover clear. Remove the motor securing screw which is located at the side of the Synchron motor.

Motor-securing screw in a Honeywell motorised valve powerhead
Synchron motor-securing screw in a Honeywell 3-port motorised valve

On the other side of the motor there is another flange which is located below a metal tab. There is no screw in this flange on the motor in a Honeywell valve.

Metal retaining tab holding flange of Honeywell valve Synchron motor
Honeywell Synchron valve motor flange secured below metal tab

Slide the blunt end of the motor sideways until the flange comes out from the tab holding it down. This can be a bit of a fiddle. The motor then comes free of the valve, held only by the two wires which connect it electrically. These two wires may be blue (in a Honeywell original Synchron motor) or orange (most replacement Synchron motors).

The wires to disconnect are the two wires which run from the motor. On earlier motorised valves, these were both joined to other wires using metal crimps encased in plastic. On more recent valves, one wire is joined with a crimp and the other is wired directly to the electrical components of the valve.

Crimps are metal tubes within plastic insulation, which are flattened using pliers to trap two wires, joining them electrically. These crimps can sometimes be re-opened by using pliers to squeeze together the edges of the flattened tube. This can be done with the plastic in place. If successful it frees the two wires. The plastic insulation may break, in which case the crimp is discarded.

If one motor wire is permanently fixed to the powerhead, you will need to cut it. Cut it closer to the failed motor, leaving a longer piece of wire connected to the powerhead. The cut end of this wire must have the insulation stripped back. The photos show how much insulation to remove.

This should have left you with a failed motor which is now disconnected from the powerhead and can be discarded. It should also have left you with two wires still connected to the powerhead.

Replacement Synchron valve motor, showing crimp and spade connectors
Replacement Synchron valve motor which has been supplied with two types of connector. The orange connectors are not used in Honeywell valves. The two white connectors are crimps

One of the wires from the powerhead must be connected (crimped) to one of the new motor wires. The other free wire from the powerhead must be connected to the other wire of the new motor. It doesn’t matter which of the two motor wires is connected to which of the two free powerhead wires as they are polarity free.

The new motor must now be fitted back into the powerhead. The small metal gear wheel on the bottom of the motor goes through a hole in the powerhead base plate. In our photo that hole has black grease round it.

The motor must then be wriggled back into place so that one of the motor flanges slides back below the angled metal tab on the powerhead.

Honeywell motorised valve motor location hole
The small gear wheel on the Synchron motor fits into the round hole which has black grease round it in this picture. One flange of the motor slides below the long metal tab at the right of the picture

The other motor flange must line up so that the single securing screw can be re-fitted and tightened. With the new motor in place, the wires must be tucked in so that they fit within the metal cover without pinching. The wires should go round the motor, not across the top of it.

Motor securing screw position in a Honeywell motorised valvel motorised valve.
When the new motor is back in place, the flange on the other side of the motor must be held below the metal tab as before. The flange on this side must be lined up with the nut as shown. The single screw can then be re-fitted and tightened.

If the powerhead was removed from the valve to make it easier to change the motor, it must now be re-attached to the valve. The power head cover can then be refitted and secured with the single screw. Make sure it sits squarely on the powerhead, with no wires pushing out from the sides.

Once the cover is back in place, the power can be re-instated and the operation of the motorised valve can be tested.

Honeywell motorised valves electrical operation

Honeywell 2-port motorised zone valves (V4043H) are electrically quite simple. The powerhead contains the motor, which is used to drive the valve open, and an auxiliary switch or end switch.

Honeywell 22mm zone valve operation (V4043H1056)

Honeywell V4043H1056 22mm 2-port zone valves have five wires: green/yellow is Earth, blue is Neutral, brown is Live (or Line) to the motor, grey and orange are connected to the end switch and form part of a separate circuit.

When a demand comes from the programmer (via the thermostat), the motor is energised and drives the valve open to allow water to pass. When the valve is fully open, a microswitch is operated in the powerhead, connecting the grey wire to the orange wire. This is called closing the switch. It sounds a bit counter-intuitive, but when a switch is closed it is completing the circuit and allowing current to pass; when the switch is opened it is opening a break in the circuit and stops current from passing.

The auxiliary circuit (grey and orange wires) is commonly used to operate the boiler and/or the circulating pump. The auxiliary circuit could be set to work at a lower voltage than mains but it is normally carrying mains voltage. It works like this: One of the two wires, typically the grey, is connected to a permanent mains Live supply (about 230V AC in the UK). The other wire, usually the orange, is connected to the Switched Live feed to the boiler.

When the programmer and stat send a Live feed to the 2-port motorised brown wire, the motor drives the valve open to allow water to pass. When the valve is fully open, the end switch closes, allowing electrical current to pass from the grey wire to the orange wire and from there to the boiler Switched Live. Unless the boiler thermostat is already up to temperature, the boiler will now fire.

With modern boilers, the boiler sends a Live feed to the circulating pump which then pumps heated boiler water through the valve. It will go to the radiators or to the cylinder coil, depending on which valve was opened. With older boilers, the Live from the auxiliary circuit end switch goes directly to the pump at the same time as it goes to the boiler Switched Live.

Using an auxiliary circuit and end switch is clever design for two reasons:

If the valve motor fails, the motorised valve will not open. The valve will not then close the end switch and so will not complete the auxiliary circuit. The boiler will not fire (with no open pipe circuit to dissipate the heat), unless another motorised valve opens another pipe circuit and calls the boiler into action. This prevents the boiler firing and the pump running when there is no water circuit open.

The auxiliary circuit allows several 2-port motorised valves to be used to control separate zones without interacting electrically. Otherwise, if several zone valves were used without auxiliary circuits, and all were connected to the same pump so that the Live wire that opened each valve also fed the pump Live, there would be problems.
As soon as a Live signal went to one zone valve to open it and to run the pump, it would feed back to the Live wire on all the zone valves, causing them all to open. All the zone valves would open and close together, defeating the purpose of separate zones.

Honeywell 28mm zone valve operation (V4043H1106)

The Honeywell V4043H1106 28mm 2-port zone valve has 6 wires. Five of these wires are the same as 22mm 2-port valve. Green/yellow is Earth, blue is Neutral, brown is Live (or Line) to the motor, grey and orange are connected to the end switch and form part of a separate circuit.

However, in the 28mm 2-port valve there is a 6th wire, coloured white. In many cases, this white wire is not used and it must simply be made electrically safe (isolated so that it cannot touch any metal component). If the white wire is not used, the 28mm zone valve is wired in the same way as the 5-wire 22mm zone valve, and operates in the same way.

It is now relatively unusual for the white wire (6th wire) of a Honeywell 2-port zone valve to be used. It is used to allow independent temperature control of both the heating and the hot water circuit where the installation has pumped heating but gravity hot water. Honeywell publish a Heating Controls Wiring Guide explaining how the controls should be wired in this case. The link will open in a new tab.

Honeywell 3-port mid-position valve operation (V4073A1039 and V4073A1088)

Honeywell V4073A1039 3-port motorised valve
Honeywell V4073A1039 22mm 3-port mid-position motorised valve showing inlet port AB and outlet ports A and B. This valve can be open to either port A or port B, or to both ports at the same time

The Honeywell mid-position motorised valve has three ports in a T configuration. Water enters via port AB. Water leaves by either port A or port B or by both at the same time. Port A is normally connected to the radiator circuit and Port B to the cylinder coil (to heat hot water). The circulating pump is usually connected to feed water from the boiler into port AB.

The explanation that follows assumes the valve is connected to the pipework in that way.

The Honeywell V4073A 3-port valve has five wires. These are blue, green/yellow, white, grey and orange. Note that the grey and orange wires are used differently from the grey and orange wires of the 2-port valve!

The blue wire is the Neutral, N. The green/yellow wire is the Earth wire, E. The white wire is connected to the wire from the room thermostat which calls for heating (radiators or underfloor). The grey wire is used to drive the valve to the Water Off position, in which only the heating port A is open; it closes port B. The orange wire provides a Switched Live (Switched Line) feed to run the boiler and pump.

Whereas the internal electrics of the 2-port valve are quite simple, the internal electrical controls of the V4073A mid-position valve are more complex.

If you want a clear explanation of the internal electrical working, see John Ward’s YouTube video. He’s really good!

Internal view of Honeywell V4073A motorised valve
Inside a Honeywell V4073A 3-port motorised valve showing the rubber ball which closes one or other port, never both.

The Honeywell V4073A is a spring-return valve. Port A or port B can be closed by a rubber ball, though never both at the same time. The rubber ball is moved between ports A and B by an actuator shaft or spindle which is driven by the powerhead. The inlet port AB can never be closed; the ball only moves between port A and port B.

The V4073A 3-port valve never closes water flow through the valve completely. There is always an open pathway from port AB to port A or from port AB to port B or from port AB to both ports A and B at the same time.

The rubber ball sits against the circular port (right side in photo), closing it off. We’re told that the ball touches one edge of the circular port first, causing the ball to rotate slightly on its spindle. This regular slight rotation evens out distortions in the ball. A little piece of elegant design work by Honeywell!

When all electrical power to the heating controls is switched off, the spring pulls the ball across to close port A, leaving port B open. This is the relaxed state or de-energised state of the valve. It is also sometimes called the Normal state.

When a V4073A mid-position valve is set up in a Y-Plan configuration and Hot Water is called for, power to the boiler is provided directly from the cylinder thermostat. The valve is not energised.

When Heating is also called for, the white wire is energised and the valve will motor to, and stop in, a mid-position. Power for the boiler is still supplied directly from the cylinder thermostat. The orange valve wire may have a potential of 230V but this is coming from the cylinder stat (to which the orange wire is also connected) and not from the circuitry of the valve.

If Hot Water is then satisfied (either by the programmer or cylinder stat), the grey wire is energised. As there is still a demand for Heating, the valve will motor to the Heating Only position (port A open; port B closed) and switch a 230V supply onto the orange wire, to power the boiler.

Only when both white and grey wires are energised (and the valve goes to the Heating Only position) can the orange wire get its 230V supply via the valve itself. (Remember, the orange wire can also get 230V from the cylinder stat if it is calling and a hot water program is on.)

When Heating Only is on, and then is switched off or the room stat demand is satisfied, a lower voltage of between 50V and 150V will remain on the orange wire. The motor will continue to be energised (though on lower power) and will remain warm. The valve will remain in the Heating Only position (port A open; port B closed). If Hot Water is turned on again, or all the mains power is turned off, the motor will be de-energised and the spring will pull the valve back to the Hot Water Only position (port A closed; port B open).

Honeywell motorised valve manual lever

Honeywell motorised valve, showing the manual lever
Manual lever on Honeywell motorised valve

Honeywell say that the manual lever located on the end of the powerhead is not a position indicator and should be used used for filling the system and for draining down only.

You set the valve into the manually open position by turning the power off, then pushing the lever towards the Man Open end of the slot. You will be pushing against the return spring. You can then lift the lever slightly and release the pressure so that the spring pushes the lever back, leaving it caught behind the hook at the top of the slot.

There is, however, more information the lever can give us if we know what we’re looking for. The lever pushes the valve open against the return spring. The valve does not pull the lever over towards the open end as the valve opens.

With the 3-port valve, port A is closed and port B is open when the valve is de-energised. This is the state either when all the power is off or when Hot Water Only is selected. In this valve position, the lever is only slack in the slot for about a quarter of the slot travel (starting at the Auto end).

If the lever is moved further to the right you can feel the strong resistance of the return spring as you force the valve open. After forcing it open, if you release the lever it will be pushed back towards the Auto end. So, if the lever is only loose for the first ¼ of the slot, the valve is in the Hot Water Only position.

When Heating and Hot Water are both selected, the valve drives open to the mid-position and stays there. The lever then becomes slack for almost the entire travel of the slot.
You should be able to feel a bit of spring resistance, right at the far end (Man Open end) of the slot.
This can be difficult to feel for at first. It is most obvious when the valve has been in the Heating Only position and reverts to the mid-position.

So, if you set the system for Heating Only (Hot Water must be off or satisfied on the cylinder stat) the valve motor drives the valve to close port B while it leaves the heating port A open. The lever will be slack across the whole length of the slot with no end resistance at all. This is because the lever can only drive the valve just a little past the mid-position but the motor drives it much further.

Knowing this, we can now feel for the mid-position (Heating and Hot Water both open).

Starting with the controls set for Heating Only, hold the lever tight against the right side of the slot. Now get someone to select Hot Water too, so you get Heating and Hot Water together. You may need to turn the cylinder stat up to make it call. As soon as Hot Water is also called, you will hear the valve start to unwind under the force of the spring, then you will feel the lever “bump” your finger.

That noise and that bump are diagnostic. They tell us that the valve has moved into the mid-position where both Heating and Hot Water ports are open. If you can make a Honeywell 3-port mid-position valve move into all three of those positions, the valve and controls appear to be wired correctly and the valve appears to be working normally.

The manual lever on the 2-port valve tells us less. If the valve is closed, the lever will be slack for up to about ⅓ of the travel of the slot. When the valve is open, the lever should be free across the whole of the slot.

Other Honeywell motorised valve faults

Honeywell valve spindle seizes up

Seized drive spindle in a Honeywell motorised valve
Drive spindle of a Honeywell motorised valve. It is accessed by removing the valve powerhead. Be warned, with Honeywell motorised valves made pre-1985 you have to drain down first to remove the powerhead!

This section also applies to most other makes of motorised valve too, not just Honeywell valves.

A failed motor will prevent the motorised valve from opening but it is not the only cause of a valve failing to open correctly. After years of use, the O rings sealing the valve spindle (or actuator shaft) can fail. When this happens, central heating water will seep past and will corrode the metals.

This can cause the valve spindle to seize. It often becomes stiff to turn at first and the valve may give intermittent problems. Eventually, the spindle may become so stiff that the valve motor cannot turn it at all.

If the powerhead (actuator) can be safely removed from the valve body (see warning above about pre-1985 Honeywell valves) you can try to turn the spindle. You may need a tool unless you have strong fingers. You must also isolate the electrical supply before removing a Honeywell motorised valve powerhead.

Old Satchwell Sunvic valve bodies used to turn through a full circle, as did Switchmaster Midi valve bodies. Honeywell and Drayton motorised valve bodies do not.

Old Satchwell Sunvic motorised valve with seized spindle
Seized motorised valve spindle in an old Satchwell Sunvic 2-port motorised valve. The water leakage has caused white oxides to form round the brass spindle, making it too stiff to turn

Honeywell and Drayton motorised valve bodies only turn through a limited arc and you must “feel” for the points at which the movement stops. The spindle in Drayton 2-port valve bodies only turns through about 30º (this angle is about 5 minutes on a clock face).

In Honeywell V4043H 2-port valves it turns through about 70º (about 11½ minutes on a clock face). In Honeywell V4073A 3-port valves it turns through about 45º (about 7½minutes on a clock face). These are all small angles!

If you need a tool to turn the spindle because it is very stiff, the valve may be failing. If it has seized up you may be able to free it temporarily by gently moving it backwards and forwards but it will probably seize up again before long.

Temporarily freeing the spindle may make water seep past the O ring seals. In our experience this has always been a very slow seepage at most. We use a small adjustable spanner across the flats on the valve spindle.

The Honeywell valves have a D-shaped top to the spindle but you can also use a spanner on this. If you do this, you must use very little force as it is very easy to shear a spindle or damage the valve internally.

Sometimes a powerhead is able to drive the valve only part way open but not far enough for the auxiliary circuit end switch to close. This valve will then not be able to tell the boiler to fire.

Where two 2-port motorised valves are fitted (one for the heating circuit and one for the hot water cylinder circuit) the fault may be disguised. Even though one valve only partly opens itself and is unable to fire the boiler, the valve on the other circuit can open fully and fire the boiler. The pump then pushes heated boiler water through both the open valve and the partially open valve.

If, for example, the heating valve is failing in this way, you will get heat round the radiators while the cylinder hot water is being heated too. When the cylinder is up to temperature, the hot water motorised valve closes and no longer tells the boiler to fire, so the heating now stops too.

If it’s the other way round, and the 2-port valve controlling the hot water circuit is failing, it may be less obvious. The heating circuit valve may be open for long periods telling the boiler to fire. If the hot water valve is partially open, you may not run out of hot water.

In summer, of course, with no heating on, this fault on the hot water valve would show up very quickly because the heating valve would not be telling the boiler to fire.

Switchmaster Midi 3-port valve body with seized spindle
A Switchmaster Midi 3-port valve body with a seized spindle. This motorised valve was also rusting through round the screw in the picture

Honeywell powerhead (actuator) jams?

Occasionally we come across a Honeywell motorised valve where the powerhead jams but the spindle (actuator shaft) is still free. Where this happens it is usually with the valve jammed open. If all the power to the central heating system is turned off, and the manual lever is still loose across the whole slot, the mechanism may be jammed.

Unless the valve is very old (pre-1985) it should be possible to remove the powerhead from the valve body without draining down. You must isolate the electrical power before removing the powerhead. When the powerhead is lifted away from the valve body, the jammed mechanism may free itself and spring back into position. If it does, the valve may work normally once the powerhead has been replaced. If the same fault repeats, it suggests that the gearing in the powerhead may be worn. We’d then change the powerhead or, if the valve spindle seems tight, change the complete valve.

List of Honeywell motorised valve types

As we’ve said above, Honeywell make a large range of motorised valves. The Normal state of a valve is the de-energised state. This is the state when no electrical power is being used by the valve motor.
A normally-closed valve is closed when no power is being applied to it and needs electrical power to drive it open.
A normally-open valve is open when no power is being applied to it and needs electrical power to drive it closed.

V4073A1039 is a 3 port, 22mm compression, 5-wire, mid-position diverter valve
V4073A1088 is a 3 port, 28mm compression, 5-wire, mid-position diverter valve
V4073A1054 is a 3 port, ¾” BSP Female threaded, 5-wire, mid-position diverter valve
V4073A1062 is a 3 port, 1” BSP Female threaded, 5-wire, mid-position diverter valve

V4043H1056 is a 2 port, 22mm compression, 5-wire, normally-closed zone valve with an auxiliary end switch
V4043H1106 is a 2 port, 28mm compression, 6-wire, normally-closed zone valve with an auxiliary end switch
V4043H1007 is a 2 port, ¾” BSP Female threaded, 5-wire, normally-closed zone valve with an auxiliary end switch
V4043H1080 is a 2 port, 1” BSP Female threaded, 6-wire, normally-closed zone valve with an auxiliary end switch

V4043C1156 is a 2 port, ½” BSP Female threaded, 3-wire, normally-closed zone valve but has no end switch
V4043B1257 is a 2 port, 22mm compression, normally-open zone valve, no manual lever, no end switch
V4043B1265 is a 2 port, 28mm compression, normally-open zone valve, no manual lever, no end switch

Honeywell V4044C1288 3-port 22mm 3-wire motorised valve
Honeywell V4044C1288 22mm 3-port diverter valve. This valve is not a mid-position valve. It opens either Port A or Port B (usually heating and hot water). Apart from the few moments when it is switching between ports, Port A and Port B are not open together. Note that it is a 3-wire valve, not a 5-wire valve

The V4043B valves are uncommon and likely to be found in solid fuel systems. These valves fail-safe in the open position in the event of a power failure or valve motor failure.

V4044C motorised valves are 3 port diverter valves. They send flow to either the hot water port or the heating port but not both, except briefly during switchover. They are 3 wire valves.

V4044C1288 is a 22mm compression, diverter valve feeding one port at a time only
V4044C1569 is a 28mm compression diverter valve feeding one port at a time only
V4044C1098 is a 3/4″ BSP Female diverter valve feeding one port at a time only
V4044C1494 is a 1″ BSP Female diverter valve feeding one port at a time only

The Honeywell motorised valve faults detailed above are likely to apply to most domestic Honeywell valves.

Much of what we describe also applies to ACL Drayton motorised valves like the Drayton 2-port ZA5/679-2 22mm zone valve and the Drayton 3-port MA1/679 22mm mid-position valve. Iflo motorised valves and British Gas motorised valves have similar faults. It may also apply to the Tower VAL222MV motorised valve, the Siemens CZV222 motorised valve and the Flomasta 27900SX motorised valve.

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